1.3.2 Wired and wireless networks, protocols and layers

Wired connections use physical cables (copper or fibre optic) and requires a NIC. They use a wired connection protocol - usually ethernet.

What are the advantages and disadvantages of wired connections?

advantages

• higher data transmission speeds

• higher maximum distance for reliable communication

• more secure - physical connection would be needed to intercept data

disadvantages

• require more space

• expensive and harder to install - require technical knowledge

• restricted movement

Wireless connection (wifi and bluetooth) use radio waves and require a WNIC.

What are the advantages and disadvantages of wireless networks?

advantages

• cheaper and easier to install - home wifi networks - automatic

• freedom of movement

disadvantages

• slower speed - signal affected by the node’s distance from the wireless access point as well as any obstacle

• lower maximum distance for reliable communication

• less secure - signal cannot be contained so data can be intercepted without authorised users knowing

When would a wired network be most suitable?

• if the devices are unlikely to need to move

When would a wireless network be most suitable?

• if the devices are likely to need to move

What is encryption and why is it needed?

• the encoding of data (plaintext) using a key so that it can no longer be understood (ciphertext)

• a key is a sequence of numbers (often a formula) that can be used to encrpt or decrypt

• it is needed as data transmitted over a network can be intercepted - encryption prevents unathorised users understanding it

• important in protecting confidential info from being accessed (to folllow legislation)

What is symmetrical encryption?

• a single private key is used to encrypt and decrypt a message

• the same key must be given to the recipient to use to decrypt

what is asymmetric encrption?

• two keys are used - one public key to encrypt and the other private key to decrypt

• more secure - you never have to reveal your decryption key

• anyone can use public key to encypt but only the private key of the recipient can decypt

What are the features of WEP and WPA?

• both are wireless encyption standards

WEP

• older

• easily broken

• no longer used

WPA

• newer

• harder to break

• more widely used now

When is encryption considered strong?

• the useful lifetime of the data is less than the time taken to decrypt it

When is encyption considered weak?

• the data can be encypted in time to use the info but wouldn’t be worth the effort trying

What is a networking protocol?

• a set of rules that govern how communication should happen within a network

What are networking standards?

• rules that allow computer systems to communicate across networks

• created to ensure devices are compatible

• ethernet (e.g) - used by mostly all manufacturers in many devices to allow for compatitbility. it became a standard due to high bandwidth, inbuilt security, a proven reliable connection low cost for installation compared to other wired connections etc

What are the advantages and disadvantages of 2.4GHz?

advanatages

• greater range and coverage

disadvantages

• more interference from other devices as it is a crowded frequency

• lower data transmission rates

What are the advantages and disadvantages of 5GHz?

advantages

• less crowded space - 23 non overlapping channels

• higher transmission rates

disadvantages

• less able to penetrate walls

What are the features of MAC addresses?

• unique string of hex

• assigned to each NIC as a serial number

• only used within a LAN

• cannot change

What are the features of IP addresses?

each device is given a unique IP address when connected to a network

IPv4

• uses a numeric dot decimal notation - 4 sets of numbers seperated by 3 dots.

• max value 255 for each set

• 32 bit - 4 billion unique addresses

IPv6

• 8 sets of 4 digits of hex

• 128 bit

What is HTTP/S used for?

• to transfer web pages over the internet so that users can view them in a web browser

• HTTPS is the more secure version as it uses encryption

What is FTP used for?

• used to transfer files over a network

• commonly used to upload or download files to and from a web server

What is SMTP used for?

• used to send emails to a mail server and between mail servers

• email software sends the email to the SMTP server used by the company or individual.

• The mail server then relays the message through various other servers.

• The email arrives at the destination mail server

What are POP and IMAP used for

both are used for receiving and storing emails from a mail server

POP

• will download every new message to your local device and remove it from the mail server.

IMAP

• syncs the message with the mail server so it can be accessed by different devices

• only removed if the user deletes them

What are TCP and IP used for?

TCP

• allows packets to be sent and received between computer systems

• breaks up data sent into packets and reassembles them at the destination

• it also checks for errors and resends lost messages

IP

• routes and addresses (gives a unique IP address to) individual packets between IP addresses

• ensures data packets sent across networks are sent to the correct destination

What is the protocol stack?

• 4 layers that enable communication

• each layer is a division of network functionality

• data moves back up the layers upon arrival

What are the roles of each layer?

the application layer -

• allows humans and software to use the network

• the application you are using determines the correct protocol to use to communicate and then display the data that has been received to the user

• HTTP/S, SMTP, FTP

the transport layer -

• creates the connection between two computers

• data is then divided innto packets and given a packet number

• packets are reassembled by the recipient’s transport layer

• TCP

the network(internet) layer -

• source and destination addresses are written on packet headers and removed by the recipient’s network layer

• routes the data packets

• the optimal route for data is calculated in this layer

• IP

the link layer -

• sets out format of packets

• handles transmission errors

• passes data onto the physical layer

• ethernet, MAC, WiFi

Why are layers used?

• self contained- the functionality of one layer can be changed without affecting other layers

• different hardware or software operates on a

  particular layer providing interoperability between

  providers and systems. manufacturer’s routers operating on the Internet layer, will operate with another manufacturer’s

  Network Interface Cards (NICs) operating on the Link layer. Senders and receivers using different software and hardware

  can communicate using the same layer protocols